Why is lighting important?
Whether in industrial or office settings, proper lighting makes all work tasks easier. People
receive about 85 percent of their information through their sense of sight. Appropriate
lighting, without glare or shadows, can reduce eye fatigue and headaches. It highlights
moving machinery and other safety hazards. It also reduces the chance of accidents and
injuries from "momentary blindness" while the eyes adjust to brighter or darker
surroundings.
The ability to "see" at work depends not only on lighting but also on:
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the time to focus on an object. Fast moving objects are hard to see.
the size of an object. Very small objects are hard to see.
brightness. Too much or too little reflected light makes objects hard to see.
contrast between an object and its immediate background. Too little contrast makes
it hard to distinguish an object from the background
What are other OSH Answer documents about lighting?
Please also see:
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Eye Discomfort in the Office
Lighting Ergonomics - Survey and Solutions
Lighting Ergonomics - Checklist
What are different sources of light?
Daylight: How much daylight reaches inside a building depends on the amount and
direction of sunlight, cloud cover, local terrain, and the season. As well, the size, orientation
and cleanliness of the windows is important. The amount of daylight entering the workplace
can be controlled with tinted glass, window blinds, curtains, and awnings. Daylight is
desirable in the workplace providing it does not cause glare or make the work area too
bright.
Remember, not enough light can also be a problem so even in workplaces where daylight is
available, it is essential to have a good electric lighting system.
Electric Lighting: The amount of light, the colour of the light itself and the colour that
objects appear vary with the type of electric lighting. The lighting must match the workplace
and the task. The following are common types of bulbs.
Table
Light Bulbs*
Type
Common
Application
Efficiency
Colour Rendering**
Incandescent
homes
poor
good
Fluorescent
offices
good
fair to good
Mercury
factories, offices
fair
fair to moderate
Low pressure sodium
roadway
good
poor
High pressure sodium
factories, commercial
good
fair to good
Metal Halide
factories, commercial
good
good
* Bulbs are often referred to as lamps in many technical publications.
** Colour rendering is the effect of light on the colour of objects.
What are basic types of artificial lighting?
There are three basic types of lighting:
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general,
localized-general, and
local (or task).
General lighting provides fairly uniform lighting. An example would be ceiling fixtures that
light up large areas.
Localized-general lighting uses overhead fixtures in addition to ceiling fixtures to increase
lighting levels for particular tasks.
Local (or task) lighting increases light levels over the work and immediate surroundings.
Local lighting often allows the user to adjust and control lighting and provides flexibility for
each user.
What are different types of light fixtures?
The complete lighting unit (also called the light fixture) controls and distributes the light.
(Light fixtures are often referred to as "luminaires" in technical publications.)
Various types of light fixtures are designed to distribute light in different ways. These
fixtures are known as:
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direct,
direct-indirect,
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indirect and
shielded (various types).
No single type of light fixture is appropriate in every situation. The amount and quality of
lighting required for a particular workstation or task will determine which light fixture is
most suitable.
Direct light fixtures project 90 to 100 percent of their light downward toward the work
area. Direct lighting tends to create shadows.
Direct-indirect light fixtures distribute light equally upward and downward. They reflect
light off the ceiling and other room surfaces. Little light is emitted horizontally meaning
direct glare is often reduced. They are usually used in "clean" manufacturing areas.
Indirect light fixtures distribute 90 to 100 percent of the light upward. The ceiling and
upper walls must be clean and highly reflective to allow the light to reach the work area.
They provide the most even illumination of all the types of fixtures and the least direct
glare. Indirect light fixtures are usually used in offices.
Shielded light fixtures use diffusers, lenses and louvers to cover bulbs from direct view;
therefore, helping to prevent glare and distribute light.
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Diffusers are translucent or semi-transparent (see-through) covers made usually of
glass or plastic. They are used on the bottom or sides of light fixtures to control
brightness.
Lenses are clear or transparent glass, or plastic covers. The lens design incorporates
prisms and flutes to distribute light in specific ways.
Louvers are baffles that shield the bulb from view and reflect light. The baffles can
be contoured to control light and decrease brightness. Parabolic louvers are specially
shaped grids that concentrate and distribute light.
Can electric lighting affect what we "see" as the colours of an object?
Yes. The "colour" of an object actually depends upon the colour composition of the light
itself as well as the colours of the light that the object reflects and absorbs.
Natural sunlight is made up of all the colours of the rainbow (spectrum) red, orange,
yellow, green, blue, indigo and violet. Most electric lights do not "make" of all these colours
even though the lights appear to be emitting "white" or "normal" light. In fact, different
lights give different colour rendering characteristics. As a result, the true colour of an object
can only be determined when viewed under sunlight or under lighting, such as full spectrum
lighting, that has the same spectral composition as sunlight.
For most work situations, colour rendering is not an issue. However, full spectrum lighting
may be needed when colour judgement is important; for example, in a fabric manufacturing
or sewing environment.
Document last updated on January 27, 2003